Parameter Estimation Device Using Differential Voltage Signals
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Solution Overview
Problem
Conventional parameter estimation devices for secondary batteries face accuracy deterioration due to the presence of an integrator element in equivalent circuit models, especially when low-frequency wave input signals are absent, leading to divergent calculations and inaccurate state-of-charge estimation.
Innovation Solution
A parameter estimation device that modifies the equivalent circuit model by replacing integrator elements with non-integrator elements, using differential voltage signals to estimate parameters, thereby improving accuracy even without low-frequency wave input signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an integrator element is used in the equivalent circuit model, then the model can represent battery behavior, but the parameter estimation accuracy deteriorates when low-frequency wave input signals are absent
Solution Approach 1:
The patent extracts and removes the integrator element from the equivalent circuit model. By eliminating the capacitor component that causes integration behavior, the model transforms from having integrator elements to using only non-integrator elements (resistors and inductors), thereby solving the accuracy deterioration problem when low-frequency signals are absent
Solution Approach 2:
The patent changes the mathematical characteristics of the model by transforming the output from voltage to its differential value. This parameter change in the output domain allows the use of non-integrator elements while maintaining the ability to represent battery dynamics, resolving the contradiction between model fidelity and estimation accuracy
2Device complexity
If conventional parameter estimation methods are used with integrator elements, then the battery model can be simplified, but divergent calculations occur and lead to inaccurate state-of-charge estimation
Solution Approach 1:
The patent converts the harmful integration effect that causes divergence into a beneficial differentiation approach. By using the differential of voltage as the output and employing non-integrator elements, the model transforms the problematic integration behavior into a stable differentiation-based estimation method, turning the original harm into a solution
Solution Approach 2:
Instead of using voltage directly as the output variable in the equivalent circuit model, the patent inverts the approach by using the differential of voltage (dv/dt) as the output. This inversion of the output variable fundamentally changes the model behavior from integration to differentiation, eliminating the divergence issue
Data Source
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AI summary
A parameter estimation device includes an input signal detecting means 3 that detects an input signal inputted to an object system 1 expressed by an equivalent circuit model 5A containing at least an integrator element Cocv, an output signal detecting means 2 that detects an output signal outputted from the object system, an output differentiating means 4 that differentiates the output signal to obtain and output an output (differential signal, a modified equivalent circuit model 5B where respective elements of the equivalent circuit model 5A are changed to non-integrator elements in such a way that the output when the input signal is inputted becomes an output differential signal, and an element parameter estimating means 5 that estimates the parameters corresponding to the respective elements based on the modified equivalent circuit model by using the signals.